Hand-held electric machine tool comprising a dust collection container and a level indicator

ABSTRACT

An electric hand-held power tool is described that has a machine housing ( 11 ) with an integral dust-ejection connection ( 15 ) and a dust collection container ( 16 ) attached thereto. To ensure, when working with the electric hand-held power tool, that the dust collection container ( 16 ) is emptied in time when full, a fill level indicator is provided that indicates, at the least, the maximum amount of dust allowed in the dust collection container ( 16 ). The fill level indicator ( 20 ) is preferably integrated in the machine housing ( 11 ) and includes a pressure sensor ( 21 ) that measures the pressure in the dust-ejection connections ( 15 ), and a display unt ( 22 ) that is actuated as a function of the pressure measured (FIG.  1 ).

RELATED ART

The present invention relates to an electric hand-held power tool according to the definition of the species in Claim 1.

With electric hand-held sanders in particular, such as orbital, oscillating or belt sanders, cloth bags, paper bags or boxes are used to collect the sanding dust, and they are slid—using an outwardly-projecting inlet connection—onto a dust-ejection connection that encloses a dust-ejection opening in the machine housing. While paper bags are designed to be disposable and to be thrown away with the collected dust, boxes have a dust collection chamber that, after the box is opened, can be emptied so the dust collection container can be reused. The inlet connection leads into the dust collection chamber, and the dust collection chamber is connected to an exhaust opening that has a dust filter in front of it.

It has already been proposed (R.304108=6955) to configure a dust collection container for an electric hand-held sander as a box with a retracted, integrated inlet connection and a dust collection chamber located above the inlet connection. The dust collection chamber is closed with a removable cover that has an exhaust opening and a dust filter located in front of the exhaust opening. The inlet connection is slid onto a dust-ejection connection formed on the machine housing, thereby resulting in a dust collection container having a compact design and short overall length.

The dust collection container fills during the sanding process. Its ability to take on more dust decreases continually and, as the suction decreases, more and more dust is released to the surroundings, which becomes increasingly more unpleasant for the operator. With belt sanders, the problem also arises that, due to the very large amount of material removed, the dust collection container fills up very quickly and, as a result, the operator usually does not notice that the dust collection container has become too full until the dust-ejection connection and other dust-transporting ducts in the device have become clogged. The device must then be taken apart to be cleaned.

ADVANTAGES OF THE INVENTION

The electric hand-held power tool according to the present invention having the features of Claim 1 has the advantage that, by way of the fill level indicator, the operator is made aware in time of the need to empty the dust collection container, thereby preventing the operator from being irritated by dust and preventing the suction ducts inside the device from becoming clogged.

Due to the measures listed in the further claims, advantageous further developments and improvements of the electric hand-held power tool described in Claim 1 are made possible.

According to a preferred embodiment of the present invention, the fill level indicator includes a pressure sensor that measures the pressure in the dust-ejection connection, the pressure sensor generating an output value that is proportional to the measured pressure, the output value corresponding to the current fill level of the dust collection container. The pressure sensor is preferably located inside the machine housing and detects the pressure in the dust-ejection connection via a duct in the machine housing that leads into the dust-ejection connection. The advantage of this is that the pressure sensor is housed such that it is protected from dust, so it cannot get dirty and therefore become inaccurate, and any type of dust collection container—including those having different volumes—can be connected to the dust-ejection connection on the machine housing without needing to adjust the fill level indicator to accommodate the particular dust collection container. The fill level indicator can therefore be used in different types of electric hand-held power tools. In the case of electric hand-held power tools with a built-in suction fan, however, the only requirement is that the fill level indicator be adjusted for the exhaust pressure produced by the suction fan in the dust-ejection connection.

Various types of commercially-available sensors can be used as pressure sensors.

According to a preferred embodiment of the present invention, an electromechanical pressure sensor with a pressure chamber bounded by a diaphragm or a displacement piston is used, the diaphragm or displacement piston including a contact element of a break contact. The pressure chamber is acted upon by the pressure in the dust-ejection connection, and the break contact is located in the circuit of an electrical display. When the diaphragm is displaced to a specified extent, the break contact closes and the display illuminates, indicating that the dust collection container has reached its maximum fill level.

DRAWING

The present invention is described in greater detail in the description below with reference to an exemplary embodiment shown in the drawing.

FIG. 1 shows a schematized, semi-longitudinal cross-section of an orbital sander with a dust collection container and a fill level indicator for the dust collection container,

FIG. 2 shows a perspective view of an electromechanical pressure sensor in the fill level indicator according to FIG. 1,

FIG. 3 shows a schematized, longitudinal cross-section of the pressure sensor in FIG. 2,

FIG. 4 shows a schematized side view of a mechanical pressure sensor for use in the fill level indicator according to FIG. 1, as a partial cross-section.

DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENT

The orbital sander shown in FIG. 1 in a semi-longitudinal cross-section as an exemplary embodiment of an electric hand-held power tool has a housing 11 in which an electric motor 12 is accommodated, the driven shaft of which drives a sanding disc (not shown) via an eccentric gear set. Mounted on the drive shaft is a fan 13 for ventilating electric motor 12, and a fan wheel 14 of a suction fan that draws dust produced when the surface of a workpiece is sanded through the sanding disc and blows it out via a dust-ejection connection 15 formed on the machine housing 11. A dust collection container 16 is connected to the dust-ejection connection 15, which can be designed as a cloth or paper bag, or as a box with a removable cover. Dust collection container 16 is slid onto dust-ejection connection 15 via a guide connection 161, and can be removed from dust-ejection connection 15 to dispose of the collected dust. Dust-ejection connection 15 is located below a U-shaped handle 17 integrally formed with machine housing 11. A push button 18 for switching electric motor 12 on and off is integrated in handle 17; when electric motor 12 is switched off, push button 18 extends into the grip opening in handle 17 and can be actuated using a finger of the hand holding handle 17.

To ensure that the operator empties dust collection container 16 filled during the sanding process in time, thereby avoiding exposure to an unnecessarily large amount of dust, a fill level indicator 20 is integrated in machine housing 11 that detects the fill level in dust collection container 16 and alerts the operator via an optical or acoustic signal at the least when the maximum allowed fill level has been reached, the signal altering the operator that dust collection container 16 needs to be emptied or replaced. Fill level indicator 20 includes a pressure sensor 21 that detects the pressure in dust-ejection connection 15, the pressure sensor generating an output value that is proportional to the measured pressure, and it includes a display unit 22 controlled by the output value of pressure sensor 21. Pressure is detected in dust-ejection connection 15 via a duct 24 leading into dust-ejection connection 15, the duct extending in machine housing 11 to pressure sensor 21 and being connected to pressure sensor 21. In the exemplary embodiment in FIG. 1, duct 24 is designed as an elastic tube 23 installed in machine housing 11 and being fastened at one end in a segment 25 located in the center of dust-ejection connection 15.

In the exemplary embodiment shown, pressure sensor 21 is designed as an electromechanical pressure sensor mounted on a printed circuit board 26 installed in machine housing 11. Further required components of fill level indicator 20 are mounted on printed circuit board 26. Electromechanical pressure sensor 21, which is available as an off-the-shelf product, is shown in a perspective view in FIG. 2 and in a schematic longitudinal cross-section in FIG. 3, to illustrate its mode of operation. Pressure sensor 21 has a housing 27 in which two housing openings 28, 29 are formed. Upper housing opening 28, at the least, as shown in FIGS. 2 and 3, is enclosed by a connecting tube 30, onto which tube 23 is slid. A diaphragm 32 is located in housing 27, diaphragm bounding a pressure chamber 31 in housing 27, housing opening 28 being located in pressure chamber 31. Housing opening 29 leads into the region in housing 27 behind diaphragm 32. A contact bridge 33 is installed on diaphragm 32, the contact bridge interacting with a contact carrier 34. Contact carrier 34 has two contact surfaces 35, 36. Each contact surface 35, 36 is contacted on a connecting pin 37, 38 that extends out of the underside of housing 27. Contact bridge 33, together with contact areas 35, 36 on contact carrier 34, forms an electrical break contact located in the circuit of the electric display unit 22 (FIG. 1). When contact bridge 33 touches contact areas 35, 36, the break contact is closed, and display unit 22 illuminates. A compression spring 38 is located between contact bridge 33 and contact carrier 34, the axial preload of which is adjustable using an adjusting screw 39 to adjust the travel of contact bridge 33 to the pressure in dust-ejection connection 15.

Electromechanical pressure sensor 21 operates as follows:

The blower pressure in dust-ejection connection 15 created by fan wheel 14 is transferred via tube 23 to pressure chamber 31 of pressure sensor 21. As dust collection container 16 fills, the pressure in dust-ejection connection 15 increases. Diaphragm 32 bulges downward (FIG. 3) and displaces contact bridge 33 against the return force of compression spring 38 in the direction of contact carrier 34. Compression spring 38 is adjusted such that, as a result of the pressure in dust-ejection connection 15 that occurs when dust collection container 16 is filled to the maximum level, diaphragm 32 displaces contact bridge 33 so far that contact bridge 33 touches contact surfaces 35, 36 and closes the break contact. As a result, display unit 22—which is located in machine housing 11 above handle 17 such that it is visible to the operator—illuminates and indicates to the operator that dust collection container 16 is full.

Instead of diaphragm 32, a displacement piston can be located in housing 27 of pressure sensor 21, the end face of displacement piston bounding pressure chamber 31. Housing opening 29 in the part of the housing bounded by the back side of displacement piston is therefore located such that it can not be closed by the displacement piston, regardless of its position.

The exemplary embodiment of pressure sensor 21 shown in FIG. 4 is a mechanical pressure sensor that can be used in place of electromechanical pressure sensor 21. This mechanical pressure sensor is also commercially available. It has a housing 40 in which a displacement piston 41 is guided in an axially displaceable manner. Displacement piston 41 bounds, with one of its end faces, a pressure chamber 42, and is sealed off from the inside wall of the housing by a sealing ring 43. Housing 40 has an opening 44 in the region of pressure chamber 42, opening 44 being enclosed by a connecting tube 45. Tube 23 leading into dust-ejection connection 15 is slid onto connecting tube 45 so that pressure chamber 42 is acted upon by the pressure in dust-ejection connection 15. An indicator bar 46 is mounted on the back side of displacement piston 41 facing away from pressure chamber 42. Indicator bar 46 has indicator markings 47 and can be seen through a window 48 formed in housing 40. As the pressure in pressure chamber 42 increases, displacement piston 41 is displaced further to the right (as seen in FIG. 4) against the return force of compression spring 49, and an ever-larger portion of indicator bar 46 becomes visible in window 48. When maximum pressure is reached in pressure chamber 42—which corresponds to the pressure in dust-ejection connection 15 when collection container 16 is filled to its maximum level—indicator bar 46 has reached the indicator markings 50 that signal to the operator that dust collection container 16 urgently needs to be emptied.

A piezoelectric pressure-measuring cell can also be used as the pressure sensor 21 in the fill level indicator 20, piezoelectric pressure-measuring cell generating an electrical signal voltage in piezoceramics that is proportional to the pressure in dust-ejection connection 15, it being possible to use the electrical signal voltage to control display unit 22. 

1. An electric hand-held power tool with a machine housing (11) with an integral dust-ejection connection (15) and a dust collection container (16) attached to the dust-ejection connection (15), characterized by a fill level indicator (20) that indicates, at the least, the maximum allowed dust load of the dust collection container (16).
 2. The electric hand-held power tool as recited in claim 1, wherein the fill level indicator (20) is integrated in the machine housing (11).
 3. The electric hand-held power tool as recited in claim 2, wherein the fill level indicator (20) includes a pressure sensor (21) that measures the pressure in the dust-ejection connection (15), the pressure sensor generating an output value that is proportional to the measured pressure, and including a display unit (22) controlled by the output value.
 4. The electric hand-held power tool as recited in claim 3, wherein the pressure sensor (21) is located in the machine housing (11) and detects the pressure in the dust-ejection connection (15) via a duct (24) in the machine housing (11) that leads into the dust-ejection connection (15).
 5. The electric hand-held power tool as recited in claim 2, wherein the display unit (22) is visible on the machine housing (11), being located preferably above a handle (17) formed on the machine housing (11).
 6. The electric hand-held power tool as recited in claim 3, wherein the pressure sensor (21) is an electromechanical pressure sensor, with which a pressure chamber (42) bounded by a diaphragm (32) or a displacement piston (41) is acted upon by the pressure in the dust-ejection connection (15) and which is preloaded via a spring (38) against the pressure in the pressure chamber (42), and a contact member of a break contact located in the circuit of an electrical display unit (22) is coupled to the diaphragm (32) or displacement piston (41), the contact member closing when the diaphragm (32) or displacement piston (41) is displaced to a specified extent.
 7. The electric hand-held power tool as recited in claim 6, wherein the maximum displacement of the diaphragm (32) or displacement piston (41) is adjusted such that, when the pressure in the pressure chamber (42) corresponds to the pressure that exists in the dust-ejection connection (15) when the dust collection container (16) is filled to the maximum level, the break contact closes.
 8. The electric hand-held power tool as recited in claim 3, wherein the pressure sensor (21) is a mechanical pressure sensor with a displacement piston (41) acted upon by the pressure in the dust-ejection connection (15), and the display unit (22) is a device that displays the displacement travel of the displacement piston (41) as the fill level amount in the dust collection container (16).
 9. The electric hand-held power tool as recited in claim 3, wherein the pressure sensor (21) is a piezoelectric pressure-measuring cell.
 10. The electric hand-held power tool as recited in claim 1, wherein a fan wheel (14) of a suction fan is located in the machine housing (11), the fan wheel (14) drawing in dust from the surface of a machined workpiece and blowing it into the dust collection container (16) via the dust-ejection connection (15). 